Jökull - 01.01.2012, Blaðsíða 75

Reviewed research article
Distal tephrochronology of NW Europe – the view from Sweden
Stefan Wastegård1 and Jane Boygle2
1Department of Physical Geography and Quaternary Geology, Stockholm University, S-106 91 Stockholm, Sweden
2School of Science and the Environment, Manchester Metropolitan University, Chester Street, Manchester M1 5GD, UK
Corresponding author: stefan.wastegard@geo.su.se
Abstract – Sigurdur Thorarinsson has inspired generations of tephrochronologists. In his thesis in 1944 he
outlined the prospect of finding ash from some of the major Icelandic eruptions in peat bogs in Scandinavia.
Since Christer Persson’s pioneering work in the 1960s, more than 15 tephra horizons have been identified in
distal peat and sediment sequences in Sweden. The most widespread tephra from the Last Glacial-Interglacial
transition (LGIT, ca. 15–9 ka BP) is the rhyolitic phase of the Vedde Ash (ca. 12.1 ka BP) which has been
found in several sites with lacustrine sediments and uplifted marine clays south of the Younger Dryas moraines.
Two significant new additions to the LGIT tephrochronological frameworks of NW Europe are the Hässeldalen
(ca. 11.3 ka BP) and Askja-S tephras (ca. 10.4 ka BP). The most significant mid to late Holocene isochrones
in Sweden are Hekla-4 (ca. 4260 BP), Hekla-S/Kebister (ca. 3720 BP), Hekla-3 (ca. 3000 BP) and Askja-
1875. Other layers have been identified in single sites and are so far less valuable as marker horizons, but are
potentially important for the future.
INTRODUCTION
The foundation of modern tephrochronology was
made when Sigurdur Thorarinsson defended his
doctoral thesis at Stockholm University College in
1944 (Thorarinsson, 1944). In his thesis about the
tephrochronology of Thjórsardalur in SW Iceland he
coined the term "tephrochronology", as originally
described in Swedish: På Island föreligga alltså
synnerligen gynnsamma förutsättningar för upprät-
tandet av en absolut geologisk kronologi baserad på
mätningar, konnekteringar och dateringar av vulka-
niska asklager. Som internationell term för en dylik
asklagerkronologi föreslår jag termen tefrokronologi
(eng. tephrochronology, fr. och ty. Tephrochronologie)
av grek. τεϕ%α, aska" (Thorarinsson, 1944, p. 6).
Translated to English: "In Iceland there are therefore
extremely favorable conditions for the establishment
of an absolute geological chronology based on mea-
surements, correlations and dating of volcanic ash lay-
ers. As an international term for such an ash layer
chronology I propose the term tephrochronology".
Although Thorarinsson devoted most of his work
to proximal settings in Iceland, he also showed a great
interest in distal tephrochronology, and already in his
thesis he outlined the prospect of finding ash from
some of the major Icelandic eruptions in peat bogs in
Scandinavia. Later, in 1981, he published a paper with
the captivating title "Greetings from Iceland – ash-fall
and volcanic aerosols in Scandinavia" (Thorarinsson,
1981). In this paper, Thorarinsson made a review of
eye-witness accounts of historical ash fall events and
dispersal of volcanic aerosols in Scandinavia. He also
described what he considered to be the first published
map of dispersal from a volcanic eruption, i.e. the ash-
fall event of Askja 1875, published by Mohn (1878).
A pioneer in the study of distal tephrochronol-
ogy of Scandinavia was Christer Persson, who, fol-
lowing an excursion to Iceland in 1962 pursued the
possibility of finding tephra in Scandinavian peat de-
posits. A number of papers followed during the 1960s
where Persson described his findings of tephra in bogs
in Sweden, Norway and the Faroe Islands (Persson,
JÖKULL No. 62, 2012 73